Pion-nucleon interaction and strange particles

Abstract

In a previous paper (1) we discussed the possibility of ascribing the non localizability of the pion-nucleon interaction to the existence of an intermediate field. In particular a simple model was presented and applied to the problem of pionnucleon scattering obtaining results equivalent to the well known ones of the extended source theory (*). The model had only a mathematical character and the quanta of the internal field had no connection with reality. The purpose of the present note is to propose a more realistic theory in which the internal quanta can be identified with existing particles. At low energy pion-nucleon interactions these particles must be present only in virtual states, thus their rest mass must be higher than the one of the pion. At high energy pion-nuclcon collisions they must be apt to be created in real states. We know that K-mesons can be created in such collisions, thus the simplest hypothesis is to take them as quanta of the internal field. As it is now well known, experimental evidence concerning all phenomena connected with K-mesons indicate that these particles are isospinors (~), while the most reasonable value for their spin seems to be zero. So if we wish an interaction lagrangian linear in the pion field u, it has to be at least quadratic in the K field. Owing to the fact that the pion is pseudoscalar, it is necessary to postulate different parities for the two K wave functions in the interaction term. This possibility seems not to be excluded by reality, as it appears now probable that both parities, + and --, are to be connected with K-mesons (~). Therefore, according to these ideas, the simplest invariant interaction lagrangian between pion and K field is: